1. Field of the Invention
The present invention relates generally to a magnetoresistive head and a magnetic recording/reproducing drive, and more particularly to a magnetoresistive head and a magnetic recording/reproducing drive made of an antiferromagnetic material having a high corrosion resistance.
2. Description of the Prior Art
A magnetic thin film such as NiFe has been conventionally used as a material of anisotropic magnetoresistive film (AMR film) for a magnetic sensor or a magnetic head. The AMR film made of NiFe originally has a structure with a plurality of magnetic domains. Therefore, in cases where the AMR film made of NiFe is used as a magnetoresistive head, a Barkhausen effect is induced in the magnetoresistive head. To avoid the Barkhausen effect, it is, for example, required to apply a bias magnetic field to the AMR film in a direction of easy magnetization for the purpose of controlling the magnetic domains to change the magnetic domains to a single magnetic domain.
As one method for changing the magnetic domains to a single magnetic domain, an exchanging bias method in which two antiferromagnetic layers 4a and 4b made of an FeMn alloy or an FeMnCr alloy (refer to U.S. Pat. No. 4,755,897) and an FeMnIr alloy (refer to Published Unexamined Japanese Patent Application (KOKAI) 4-162207) or another FeMn-X alloy (refer to Published Unexamined Japanese Patent Application (KOKAI) 4-211106) are used is disclosed. As shown in FIG. 1, the antiferromagnetic layers 4a and 4b are formed on both ends of a surface of an NiFe film 3 which functions as an anisotropic magnetoresistive film. A region between the both ends is to be a sense region SA. Surfaces of the layers 4a and 4b are in contact with the surface of the NiFe film 3 to set a group of antiferromagnetic layers 4a and 4b and the NiFe film 3 in an exchanging coupling condition. The magnetization of the NiFe film 3 is oriented in a single direction by using the exchanging coupling. In this case, as shown in FIG. 1, the NiFe film 3 is formed on a ground layer 2 which is made of a nonmagnetic metal and is formed on a substrate 1. A pair of electrodes 5a and 5b for leading a sense current to a magnetoresistive head are formed on the antiferromagnetic layers, 4a and 4b (or FeMn films 4a and 4b).
Also, because the sensitivity of the magnetic sensor and the magnetic head has been recently heightened, a giant magnetoresistive film (GMR film) is watched to obtain a higher output power. In particular, as shown in FIG. 2, a spin valve magnetoresistive film has been recently watched because the spin valve magnetoresistive film can be comparatively easily produced, and a changing rate of an electric resistance in the spin valve magnetoresistive film is high in case of a low magnetic field. In the spin valve magnetoresistive film, an angle between magnetizing directions of two magnetic thin films changes with the intensity of a magnetic field applied to the spin valve magnetoresistive film, and the electric resistance changes with the angle. A phenomenon that the electric resistance changes with the angle is called a spin valve effect.
As a magnetoresistive (MR) head is shown in FIG. 2, two soft magnetic thin films such as NiFe films 13 and 15 are used as two magnetic thin-film layers, and an antiferromagnetic layer 16 made of an FeMn alloy is formed on a first soft magnetic layer 15. Also, a second soft magnetic layer 13 and the first soft magnetic layer 15 are laminated with a nonmagnetic metal layer 14 therebetween. Also, the second soft magnetic layer 13 is arranged on a ground layer 12 which is arranged on a substrate 11, and a pair of electrodes 17a and 17b for leading a sense current to the MR head are formed on the antiferromagnetic layer 16.
A bias magnetic field Hua of the antiferromagnetic layer 16 is applied to the first soft magnetic layer 15 to fix a magnetizing direction of the first soft magnetic layer 15. A magnetizing direction of the second soft magnetic layer 13 is rotated with a signal magnetic field. Because of the rotation of the magnetizing direction of the second soft magnetic layer 13, an angle .crclbar. between the magnetizing directions of the first and second soft magnetic layers 13 and 15 changes. A whole resistance of the MR head changes in proportion to a cosine of the angle .crclbar.(cos .crclbar.). In this case, a sense current is supplied to the MR head through the electrodes 17a and 17b. The change of a voltage between the electrodes 17a and 17b is detected to obtain the whole resistance.
However, because corrosion resistance of the antiferromagnetic layer 16 (or FeMn film 16) is low, the yield rate of the MR head is lowered, the number of manufacturing steps increases, and the reliability for the MR head is lowered.
To avoid the above drawbacks, it is disclosed in U.S. Pat. No. 5,315,468 that an NiMn alloy is used as the antiferromagnetic layer in place of the FeMn alloy. However, a heating process for the NiMn film is required to obtain the bias magnetic field, with a heating temperature of no less than 260.degree. C. Therefore, in case of a spin valve film or an artificial lattice film, where an NiFe film is used as the soft magnetic layer to obtain a comparatively high magnetoresistive effect and Cu is used as the nonmagnetic metal layer, Cu is diffused into and mixed in the NiFe film to degrade a magnetic resistance property thereof. Therefore, there is a drawback that a desired magnetoresistive effect cannot be obtained.
Also, the use of a PdPtMn alloy as an antiferromagnetic substance is disclosed in Published Unexamined Japanese Patent Application (KOKAI) 6-314617. However, an intensity of the bias magnetic field obtained by the use of the PdPtMn alloy becomes very low.